Tom Losh

“Do not confuse "duty" with what other people expect of you; they are utterly different. Duty is a debt you owe to yourself to fulfill obligations you have assumed voluntarily. Paying that debt can entail anything from years of patient work to instant willingness to die. Difficult it may be, but the reward is self-respect.
But there is no reward at all for doing what other people expect of you, and to do so is not merely difficult, but impossible. It is easier to deal with a footpad than it is with the leech who wants "just a few minutes of your time, please—this won't take long." Time is your total capital, and the minutes of your life are painfully few. If you allow yourself to fall into the vice of agreeing to such requests, they quickly snowball to the point where these parasites will use up 100 percent of your time—and squawk for more!
So learn to say No—and to be rude about it when necessary. Otherwise you will not have time to carry out your duty, or to do your own work, and certainly no time for love and happiness. The termites will nibble away your life and leave none of it for you.
(This rule does not mean that you must not do a favor for a friend, or even a stranger. But let the choice be yours. Don't do it because it is "expected" of you.)”
― Robert A. Heinlein, Time Enough for Love

“Knowledge was like an instantly addictive drug, and once you had one hit, you needed it always.”
― C. Gockel, Starship Waking

“It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so, and will follow it by suppressing opposition, subverting all education to seize early the minds of the young, and by killing, locking up, or driving underground all heretics.”
― Robert A. Heinlein, Time Enough for Love

“I was not giving answers. I was trying to shake the reader loose from some preconceptions and induce him to think for himself, along new and fresh lines. In consequence, each reader gets something different out of that book because he himself supplies the answers... It is an invitation to think -- not to believe.”
― Robert A. Heinlein